Conference switching system



United States Patent [72] Inventors Berry .1. Wlmberly Falls Church, Virginia 40047 [21 Appl. No. 708,390 [22] Filed Feb. 26, 1968 [45] Patented Dec. 1, 1970 73 l Assignce American Telephone and Telegraph Company, New York, N.Y., a corporation of New York [54] CONFERENCE SWITCHING SYSTEM Iii-"E1 e wsc KEYS & LAMP'S OOOOOOOOO ROTARY DlAL TOUCH TONE DIAL [1C1 DUE! EIEIU ROTARY DIAL TALK BACK AMPL TALK BACK AMPL TRUI TOUCH TONE Assistant Examiner-David L. Stewart Attorneys-N. S. Ewing and James Warren Falk ABSTRACT: A communication switching system is arranged to conference a group of line circuits and one trunk circuit via a common bus. Additional trunks may be added to the conference by connecting one terminal of a bridge circuit to the common bus while connecting a second terminal of the bridge to another bus associated with the common bus. The connection of the bridge circuit with the common bus automatically transfers the previously connected trunk circuit to the other bus, thereby interposing the bridge circuit into the conference connection between the trunk and the common bus. Echo suppression circuitry, individual to each terminal of the bridge circuit, is inhibited upon the connection of a trunk circuit which does not require external echo suppression.

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